1. Field of the Invention
This invention relates to a process for preparing an extended tonal range pre-press proof of an original color subject using photographic color print paper.
Specifically, the method is an improvement over the procedures illustrated and described in my prior U.S. Pat. No. 4,553,835, issued Nov. 19, 1985 and entitled "Process for Producing Pre-Press Color Proofs".
In particular, this invention further extends the tonal range of the process illustrated and described in the '835 patent in that it provides a relatively close match to the tonal values of the original including those which must be produced by pin dots in a lithography reproduction.
2. Description of the Prior Art
In the '835 patent, a process is described for preparing a pre-press color proof using color print paper which provides a tonal range that substantially matches the solid colors, the three-quarter tone (approximately 75%), the mid-tone (approximately 50%), and the quarter-tone or highlight detail (about 25%) values of the original artwork. The shadow areas (100%-75%) and tones of the original artwork were reproduced in the pre-press proof process of the '835 patent by separately placing the yellow, magenta and cyan negatives on the undeveloped color print papers and sequentially exposing each through blue, green and red filters respectively.
Further, in the '835 patent, mid-tone and highlight quarter-tone areas of the original artwork were reproduced in the pre-press proof process by placing on the undeveloped color print paper when the magenta separation negative is associated therewith, the magenta separation positive; the yellow separation positive on the print paper when the yellow separation negative is associated therewith; the cyan separation positive on the print paper with the cyan separation negative; and in each instance passing light through green, blue and red filters respectively for time periods sufficient to cause the mid-tones and quarter-tones to be duplicated in the final pre-press proof.
However, it was found that the procedure of the '835 patent did not always reliably reproduce the extreme highlight areas which must be printed lithographically with pin dots of varying diameter and spacing. This was especially true as to areas which vignetted from slight detail to none which can be lithographically reproduced only by very fine dots which fade into no dot at all. Specular reflections, sharp drop-outs and images which require dot vignettes for matching of original artwork are very difficult to accurately reproduce in a prepress proof. To solve the difficulty, a procedure has now been developed as described herein to obtain that important detail of tone values in the proof.